of or pertaining to Dionysos (Latin Dionysus), Greek god of wine and revelry, identified with Roman Bacchus. His name is of unknown origin. Or in reference to historical men named Dionysius such as the tyrants of Syracuse and especially Dionysius Exiguus (see A.D.), such as Dionysian period of 532 Julian years, when the moon phases recur on the same days of the week.